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Seismological Analysis of the Stars ? Serpentis and ? Leonis: Stellar Parameters and Evolution
In order to assess the information that will be available from targetsof the Microvariability and Oscillations of Stars (MOST) satellite, weexplore the possible evolutionary status and perform preliminaryseismological analysis of two targets: the stars ? Ser and ?Leo, which show solar-like oscillations. Taking into account theastrometric observational constraints on the stars, we find that ?Ser is in the main-sequence phase of evolution, while ? Leo has twodistinct solutions that match well with observations: main-sequencemodels and post-main-sequence models. The evolutionary tracks cover thefollowing ranges of mass and initial metallicity: ? Ser, 1.15-1.20Msolar and Z=0.0135+/-0.003 ? Leo, 1.62-1.70Msolar and Z=0.024+/-0.002 (for values of the Galactic heliumenrichment ratio ?Y/?Z in the range 0-2). By combiningstellar models with observational constraints, we determine age rangesof 3.2+/-0.6 Gyr for ? Ser and 1.7+/-0.2 Gyr for ? Leo. Theresults show that the masses and ages of the stars are very sensitive tometallicity and evolutionary phase. Furthermore, we find that modelswith overshooting from a convective core predict a larger age for agiven mass. Finally, we discuss future prospects for constrainingstellar models with the help of asteroseismic observations.
| A large, complete, volume-limited sample of G-type dwarfs. I. Completion of Stroemgren UVBY photometry
Four-colour photometry of potential dwarf stars of types G0 to K2,selected from the Michigan Spectral Catalogues (Vol. 1-3), has beencarried out. The results are presented in a catalogue containing 4247uvby observations of 3900 stars, all south of δ = -26deg. Theoverall internal rms errors of one observation (transformed to thestandard system) of a program star in the interval 8.5 < V < 10.5are 0.0044, 0.0021, 0.0039, and 0.0059, respectively, in V, b-y, m_1_ ,and c_1_. The purpose of the catalogue, combined with earliercatalogues, is to allow selection of a large, complete, volume-limitedsample of G- and K-type dwarfs, investigate their metallicitydistribution, and compare it to predictions of various models ofgalactic chemical evolution. Future papers in this series will discussthese subjects.
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